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Capenhurst selected as interim storage site for submarine reactor vessels

The Ministry of Defence (MoD) has selected the Capenhurst Nuclear Services (CNS) site in Cheshire as the preferred site to store radioactive reactor pressure vessels (RPVs) from dismantled nuclear submarines. The selection of a site concludes a process begun in 2012 and means that decommissioning work can begin on the submarines.

The selection process considered all existing nuclear sites in the UK before producing a shortlist of five sites: Capenhurst, the two Atomic Weapons Establishment sites, Aldermaston and Burghfield, plus Sellafield and Chapelcross. The RPVs will removed from the submarines at their current storage locations in Rosyth and Devonport naval dockyards, and transported to the chosen site, where they will be stored until they can be disposed of in the Geological Disposal Facility (GDF) which the government hopes to construct for the storage of the UK's radioactive waste legacy.

The MoD's preferred option is that the store for the RPVs will be housed in an existing facility at Capenhurst, but if that is not possible then a new facility will be built. In the event that the MoD is not able to agree a contract with CNS then the contingency site will be Aldermaston.

The decision was made using a multi-criteria decision analysis process which incorporated policy, operational, health & safety and environmental factors as well as whole life costs and the responses from public consultation on the short-listed sites. The risk of flooding at Burghfield was cited as an external hazard, though the proposed site of the store would have been in a part of the site not thought to be at risk from flooding. Siting the store at either AWE site was judged likely to have a detrimental effect on other MoD operations at the sites. As other construction work at Aldermaston is already significantly behind schedule, this finding is unsurprising.

Chapelcross was judged to have numerous disadvantages, including the opposition of the Scottish Government and local authorities. Sellafield was unable to identify a specific site for the store, and the MoD acknowledged that there is a perception that Sellafield is seen as the 'default' site for holding the UK's radioactive waste legacies and that storing extra waste there would set an unwelcome precedent.

A major reason for choosing Capenhurst was the possibility of using an existing facility, which will greatly reduce the impact and cost of the project. Storing waste was also considered to fit well with CNS's 'mission'. Capenhurst has served as the uranium enrichment plant for the UK's nuclear programme since the 1950s, and commercial uranium enrichment continues at the site for use in nuclear power stations. However, decommissioning work is underway at the site and there are long term plans to store 60,000 tonnes of depleted uranium in part of an old gaseous diffusion plant until 2150. It seems likely that the proposed store for the submarine RPVs is in the same building.

The length of time the RPVs will be kept in interim storage depends on the speed at which a GDF can be built. For every site on the shortlist there were consultation responses that expressed skepticism about the planned 2040 opening date for the GDF. The MoD response to these concerns acknowledges the possibility that work on a GDF will take longer than current projections and that that materials with a higher level of radioactivity than the RPVs would be likely to be higher up the queue for disposal.

Currently no site has been selected for a GDF, despite the process having begun in 2008, and the only sites currently under consideration have been vetoed by Cumbria County Council. Although the RPVs are classified as Intermediate Level Waste (ILW), the GDF will also need to store High Level Waste (HLW) and at present no deep geological HLW facility has been built anywhere in the world. The MoD have dealt with this uncertainty by making plans to store the submarine wastes at Capenhurst until 2120 if necessary and the consultation response acknowledges the fact that the situation could be characterised as indefinite, rather than interim, storage.